This application is directed to new and improved nozzles systems for plural component spray guns most particularly nozzle systems which utilize both a secondary fluid stream and a secondary gas stream, emitted from separate orifices, to assist in shaping a resin fan and to transfer catalyst to the resin fan.
A facile way of forming Fiberglas articles is achieved by spraying resin and catalyst precursor components of the Fiberglas against molds, mandrels and the like. A variety of spray devices have been devised for spraying of the Fiberglas components. Older spray systems utilize air to atomize and carry the resin and catalyst components from the spray gun. More modern devices utilize what is termed "airless" spraying.
In an airless spray device hydraulic pressure of a liquid component is utilized to propel the liquid component from the spray device and atomize the same. These airless systems have certain advantages over the older compressed air systems as, for instance, better control of the spray pattern and less dispersion on of the resin and catalyst components into the atmosphere.
Spray devices for spraying the resin and catalyst components of a plural component system can also be characterized as either achieving mixing of the catalyst into the resin within the interior of the spray device or exterior of the spray device. There are certain disadvantages with respect to interior mixing of the resin and catalyst components, since ultimately the catalyst causes polymerization of the resin. Because of polymerization, interior mixing devices are prone to clogging and therefore they must be cleaned out after each use prior to polymerization of the resin and catalyst.
If an operator is using such an internal mixing spray device and continuous ejection of the plural components from the gun is not maintained, when spraying is halted any mixed components remaining in the gun will polymerize. Thus, if the spray gun is not to be used for continuous operation it must be cleaned whenever spraying will be suspended for anything more than a short period of time. Cleaning is normally done by spraying an organic solvent such as acetone or the like through the interior of the spray device. This not only increase the economics of use of these devices, but present environmental hazards because of the evaporation of solvents into the work environment and into the atmosphere in general.
Additionally, if the components of the Fiberglas system are not maintained at equal pressures within the device mixing chamber one or the other of the components can contaminate the feed line of the other component. This can cause polymerization not only in the device mixing chamber but also in other areas of the device including the feed lines. Needless to say, when this happens a major clean up is necessary and in extreme cases the device can be rendered totally useless.
Externally mixing plural component spray devices eliminate the problems associated with internal mixing devices. They can, however, generate other problems. Since the catalyst is mixed with the resin exterior of the spray device inefficient mixing can occur and/or excessive amounts of toxic catalyst and the like can be lost to the atmosphere of the work environment. This is not only very uneconomical, but it is very hazardous to the operators of these devices.
In designing spray devices for plural components systems it is evident that consideration of many factors must be taken into account. In order to eliminate the use of excessive amounts of solvents and/or polymerization within the spray device, exterior mixing spray devices are preferred over interior mixing spray devices. In order to eliminate excessive vaporization of plural components, efficient low pressure airless devices are preferred over either high pressure airless devices and/or air sprays. In order to insure efficient mixing of catalyst and resin components and to achieve desirable flow patterns for applying uniform coats of the plural component system, proper choice of nozzle orientation, nozzle sizes and spray patterns must be considered. Additionally, in order to eliminate excessive waste and/or hazardous discharge of catalyst, resins and the like to the work place environment, the above nozzle characteristics as well as others must be taken into consideration
An exterior mixing plural component spray device is shown in British Patent Specification No. 735,983, filed Sept. 14, 1953 in the name of Stanley Gustav Dehn. In this device resin is sprayed and is entrained within an enveloping air shroud. Catalyst is then injected into this enshrouded resin stream at a 90.degree. angle to the ejection axis of the resin. This requires the catalyst stream to pass through an atomizing air barrier prior to mixing with the resin. As a result of this a significant amount of catalyst can be deflected into the atmosphere. Control of the spray pattern ejected from such a device is difficult because of the impinging angle of the catalyst stream on the air enshrouded resin stream.
A further external mixing plural component spray nozzle is shown in U.S. Pat. No. 4,618,098 dated Oct. 21, 1986 to Hedger et al. This patent contains a good summarization of prior spraying devices and problems associated with those devices in spraying the resin and catalyst components of Fiberglas systems. In this patent a nozzle system is shown which utilizes opposing air streams to initially shape a resin fan. After the fan is shaped by the air streams, catalyst steams are subsequently injected into the fan down stream from the air streams. Both the air stream and the catalyst stream are injected from "wings" which project forward out of the nozzle body. While this structure certainly is utilitarian, catalyst is still mixed into the resin fan several inches from the spray tip and the mixing is accomplished down stream from an initial air injection into the resin fan. Any rebound from the air stream hitting the resin fan would serve to disperse and distort the catalyst stream since it is ejected exterior of the air stream.